Earlier this month, the Food and Drug Administration assured consumers they could continue to eat rice cakes, rice pasta, brown rice dishes and other popular products in moderation, with no immediate effects from arsenic in the grain.

Agency officials offered one caution, though, suggesting that parents of infants and toddlers vary the grains in their children’s diets and limit servings of rice cereal.

But critics of the agency say it buried a more significant message: The FDA is still working on the question of whether lifelong consumption of arsenic in rice raises potential health threats such as cancer. The agency estimates it will have preliminary assessments ready sometime in 2014.

“The fact that the message they led with is good news, there is no short-term problem, is just stating the obvious,” said Urvashi Rangan, Consumers Union’s director of consumer safety and sustainability.

Although Consumers Union praised the FDA for its message of moderation to rice eaters, Rangan said the agency should have stressed that test results from 1,300 samples over two years showed inorganic arsenic “is present at varying and sometimes very high levels in the products.” That means “those things come with risks,” she said. “The question is, how much risk we are willing to take on, especially for people who consume a lot of these things?”

Jenny Levin, public health advocate for the consumer advocacy group U.S. PIRG, said the FDA’s initial test result “only affirms the concerns we’ve had in the public health community about the widespread exposure to potentially harmful levels of arsenic in rice.”

As an advocate, Levin said, the results show a “need to put in place some guidance, whether it is 10 parts per billion like it is for water. That seems reasonable. As a public health advocate, I would put it lower, at 5 parts per billion.”

But she acknowledged that an advocate’s approach “is really not FDA’s style. They like to be able to draw a direct link between a health impact and an environmental cause or a contaminant in our food supply.”

The agency says it is working methodically to do so with rice.

“The FDA has been monitoring arsenic levels in rice for more than 20 years and has seen no evidence of change in levels of total arsenic in rice. This new data is the latest of the FDA’s ongoing efforts to understand and manage possible arsenic-related risks associated with the consumption of these foods in the U.S. marketplace,” according to an FDA press release.

There are two types of arsenic — organic, or naturally occurring, and inorganic. Organic arsenic is generally considered less toxic. Inorganic arsenic, a byproduct of mining, smelting, pesticides and other industrial uses, is classified as a carcinogen and is viewed as more toxic because it accumulates in tissues and organs.

Rice is a main food staple for about half the world’s population and the second-most-consumed food grain after wheat, according to the Economic Research Service, an arm of the U.S. Department of Agriculture. Rice is also a significant agricultural export for the United States. Farmers in six states — Arkansas, California, Louisiana, Mississippi, Missouri and Texas — grow the nation’s rice crop. Thailand, Vietnam and India are the main foreign suppliers to the United States.

Arsenic in rice is prevalent enough around the world that the World Health Organization and the Food and Agriculture Organization of the United Nations are trying to reach an international consensus on setting maximum limits and deciding whether those limits should apply only to inorganic arsenic or to the combined rates for both forms of arsenic.

Last year, arsenic levels in food attracted the attention of several House Democrats. Henry A. Waxman, ranking Democrat on the House Energy and Commerce Committee, and Diana DeGette, ranking Democrat on the panel’s oversight subcommittee, went so far as to request that several food companies provide information on what steps they were taking to reduce inorganic arsenic levels in their rice products.

Deborah Willenborg, spokeswoman for the USA Rice Federation, said advocates for FDA action should pay attention to the difficulty the international organizations face in gathering reliable information on which to base arsenic restrictions.

“At this time it would be premature to establish limits since, as FDA has said, they must complete their risk assessment before such a decision can be made,” Willenborg said via email.

“Globally, we don’t know what the levels are in rice from various countries. We don’t know how and to what extent the levels can be lowered, or if it can be done without disrupting a major staple in the food supply of the world,” she added.

The federation, which represents rice growers, millers and retailers, will continue to work with the FDA on ways to reduce arsenic rates. The industry is conducting its own studies, with some results due in 2014.

On Sept. 6, the FDA released results for inorganic arsenic in 1,300 rice products it tested and concluded that the inorganic arsenic levels are not high enough for people to stop eating rice.

The highest-scoring product, brown rice syrup, registered inorganic arsenic levels of 7 micrograms or 7 parts per billion. The maximum level for water processed by water treatment plants is 10 micrograms or 10 parts per billion.

Consumers Union and its parent organization, Consumer Reports, have differed with the FDA in the past over the pace of the agency’s deliberations on inorganic arsenic in food. Last year, Consumer Reports published results of its own lab tests that found high levels of arsenic and lead in fruit juices and rice. The popular “Dr. Oz Show” took up the issue and Consumers Union campaigned for federal action.

Reps. Frank Pallone Jr., D-N.J., and Rosa DeLauro, D-Conn., said the reports raised concerns about whether the FDA would set federal limits on the toxic metals. Pallone introduced legislation, but it died in the 112th Congress. However, two months ago, the FDA proposed setting the inorganic arsenic limit for apple juice at the same level as water. The agency has extended the comment period through Nov. 12.

DeLauro said questions remain about the long-term effects of arsenic in rice. She did not indicate whether she would pursue legislation as a way to prod the FDA to faster action. Pallone’s office said the lawmaker may retool his arsenic and lead bill and file it by the end of this year.

While there is some dissatisfaction with the FDA’s approach to arsenic in food, Jerome Paulson said the agency is being responsible in its message about rice consumption, especially in the young.

Paulson, a physician and chairman of the Council on Environmental Health at the American Academy of Pediatrics, said the levels of inorganic arsenic present in the foods the FDA tested are low, especially compared to Bangladesh, Chile and Taiwan. In those countries, Paulson said, inorganic arsenic is at such high levels in ground water that decades of consumption can lead to skin lesions as well as bladder and lung cancers.

“Certainly, this is not ‘Arsenic and Old Lace’ where you drink a cup of tea then you keel over and die,” Paulson said, referring to the play and movie where arsenic is used as a poison. “We’re not at that level.”

The academy does strongly suggest that parents moderate their infants’ intake of rice cereal, but Paulson said that is a precautionary message since young children in the United States typically only eat rice cereal for less than a year.